Field-effect transistor is a transistor device which controls a current transport process in the element by a gate voltage. Back gate SOI structure-based metal-oxide-semiconductor field-effect transistor (MOSFET) has advantages of simple structure, low electrical field, high transconductance and good short-groove characteristics, and its back substrate can be used as the back gate while a back gate voltage is used to regulate and control a width of the conductive groove. Technology of the field-effect transistor is very mature, however, due to three-terminal construction of the device, a gate supply is required to be provided exclusively and its integration is complicated. Moreover, pressure sensing devices based on this type of field-effect transistor lack a direct interaction mechanism between external environment and the electronic devices.
Piezoelectric effect is a phenomenon of internal potential when a piezoelectric material is deformed under stress. For zinc oxide, gallium nitride, cadmium sulfide and other piezoelectric semiconductor materials, the piezoelectric effect can change transport properties of the interface barrier and p-n junction of metal semiconductor, which is the piezotronic effect. The piezotronic effect is actually a combination of a piezoelectric effect and a semiconductor effect. The piezotronic effect is used to convert the mechanical action applied to the device into local electronic control signal to achieve an improved method of regulating the piezo-potential as gate voltage, driving and controlling the electronic devices, micro nano mechanical devices and sensors by strain, stress or pressure.
Piezotronic transistor and traditional field-effect transistor have different working principles and structures. In principle, the traditional field effect transistor uses an external-applied voltage as control signal, while the piezotronic transistor produces electrical control signal by mechanical deformation. In the structure, the traditional field effect transistor is a three-terminal device, while the piezotronic transistor is a two-terminal device which has a virtual third terminal replaced by an external-applied pressure, to achieve the control of the transmission characteristics. These characteristics of the piezotronic transistor can reduce the gate electrode in the traditional transistor, and achieve a direct interaction between mechanical pressure and electronic devices, and its application scope will include artificial intelligence, human-computer interaction, biological medical, communication and the likes. However, the piezoelectric electronics transistor must be prepared by piezoelectric material, and, the regulation property of its produced piezo-potential and material selection and applications are subject to many restrictions.
In recent years, Professor Zhong Lin Wang in Beijing Institute of Nanoenergy and Nanosystem, Chinese Academy of Sciences and Georgia Institute of Technology proposed a concept of triboelectric nanogenerator. The triboelectric nanogenerator is based on the triboelectrification effect and electrostatic induction. Two kinds of high molecular polymer film coated with metal electrodes are attached together to form a device. This device will have a mechanical deformation under the action of external force and thus cause mutual friction between the two layers of polymer films, resulting in charge separation and formation of a potential difference. The potential difference not only can be used for self-powered active pressure sensor, but also can be used as a control signal of semiconductor devices.